Resonant scanning mirror with inertially coupled activation

ABSTRACT

A system and method for providing a resonant beam sweep about a first axis. A mirror or reflective surface supported by a first pair of torsional hinges is driven into resonant oscillations about the first axis by inertially coupling energy through the first pair of torsional hinges. A light source reflects a beam of light from the mirror such that the oscillating mirror produces a beam sweep across a target area. The resonant beam sweep is moved orthogonally on the target area by a gimbals portion of the mirror pivoting about a second axis according to one embodiment. A second independent mirror provides the orthogonal movement according to a second embodiment.

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/394,321, filed on Jul. 8, 2002, entitled ScanningMirror, which application is hereby incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention relates generally to projection displaysand laser copiers. More specifically, the invention relates to the useof MEMS (micro-electric mechanical systems) type mirrors (such astorsional hinge mirrors) to provide resonant scanning of a light beam ona display screen or on a photosensitive medium. The resonant scan may begenerated by using a single dual axis mirror or two single axis mirrors.A first set of torsional hinges is used for providing the resonant scanby oscillating the mirror about the torsional hinges at the mirror'sresonant frequency if a dual axis mirror is used. Alternately, a firstone of two single axis mirrors may be driven to resonance about itstorsional hinges to provide the bi-directional scan. The second pair oftorsional hinges of the dual axis mirror or the second single axismirror provides movement about a second axis to control movement of theresonant beam sweep or scan in a direction orthogonal to the resonantscanning to maintain closely spaced parallel image lines on theprojection display or photosensitive medium.

BACKGROUND

[0003] Although rotating polygon scanning mirrors are typically used inlaser printers to provide a beam sweep or scan of the image of amodulated light source across a moving photosensitive medium, such as arotating drum, there have also been prior art efforts to use a much lessexpensive flat mirror with a single reflective surface, such as a mirroroscillating in resonance, to provide the scanning beam. Unfortunately,these prior art efforts of using a scanning or oscillating mirror haverequired a compromise in performance in that only one direction of theresonant beam sweep could be used to print an image line at a rightangle on a page. For example, to generate image lines that are at aright angle to a moving photosensitive medium, the scanning mirrorgenerating the beam sweep is typically mounted at a slight angle tocompensate for the movement of the photosensitive medium. It will beappreciated that the photosensitive medium typically moves at a rightangle with respect to the beam sweep (such as a rotating drum).Unfortunately, if the mirror is mounted at a slight angle to compensatefor medium movement during the forward beam sweep, the return beamsweeps will traverse a trajectory on the moving photosensitive drumwhich will be at an angle which is unacceptable with the first printedimage line since the effect of the moving medium and the angle mountingof the mirror will now be additive rather than subtractive.Consequently, unlike the present invention, when such a singlereflecting surface resonant mirror was used with these prior artefforts, it was necessary to interrupt the modulation of the reflectedlight beam and wait for the mirror to complete the return sweep or cycleand then again start scanning in the original direction. Thisrequirement of only using one of the sweep directions of the mirror ofcourse reduces the print speed and requires expensive and sophisticatedsynchronization between the mirror and the rotating drum.

[0004] The assignee of the present invention has recently developed adual axis mirror with a single reflection surface described in U.S.patent application Ser. No. ______ and entitled “Laser Printer ApparatusUsing a Pivoting Scanning Mirror”. This dual axis mirror uses a firstset of torsional hinges for providing oscillating beam sweep such as aresonant beam sweep and a second set of torsional hinges thatselectively moves the oscillating beam sweep in a direction orthogonalto the oscillating or resonant beam sweep. By dynamically controllingthe orthogonal position of the beam sweep to compensate for movement ofthe photosensitive medium, both directions of the resonant beam sweepmay be used to print parallel image lines. Alternately, two single axismirrors can be arranged such that one mirror provides the resonant beamsweep and the other mirror controls the orthogonal position of the beamsweep to allow both directions of the resonant beam sweep to be used forprinting.

[0005] It will also be appreciated by those skilled in the art that inaddition to laser printing, control of the orthogonal (vertical)position of the oscillating or resonant scan allows a single surface orflat oscillating mirror to be used to provide a full frame of rasterscans suitable for use on projection displays including micro projectiondisplays such as cell phones, Personal Digital Assistants (PDA's),notebook computers and heads-up displays. However, if such displays areto be commercially acceptable, they must be small, low cost, robustenough to withstand greater than 1000 G's of shock, and stable over theoperating temperature normally experienced by hand-held products.

[0006] Consequently, it will be appreciated that the high frequencyscanning mirror is a key component to the success of such products.Further, since many of the applications for such mirror projectiondisplays are battery powered, all of the components (including thescanning mirror) must be energy efficient.

[0007] Texas Instruments presently manufactures a two axis analog mirrorMEMS device fabricated out of a single piece of material (such assilicon, for example) typically having a thickness of about 100-115microns using semiconductor manufacturing processes. The layout consistsof a mirror having dimensions on the order of a few millimeterssupported on a gimbals frame by two silicon torsional hinges. Thegimbals frame is supported by another set of torsional hinges, whichextend from the gimbals frame to a support frame or alternately thehinges may extend from the gimbals frame to a pair of hinge anchors.This Texas Instruments manufactured mirror with two orthogonal axes isparticularly suitable for use with laser printers and/or projectiondisplays. The reflective surface of the mirror may have any suitableperimeter shape such as oval, rectangular, square or other.

[0008] Similar single axis mirror devices may be fabricated byeliminating the gimbals frame altogether and extending the single pairof torsional hinges of the mirror directly to the support frame orsupport anchors. Two single axis mirrors rather than one dual axismirror may be used to generate the beam scan but may require more space.Other suitable designs of single axis mirrors may also be used.

[0009] One presently used technique to oscillate the mirror about afirst axis is to provide electromagnetic coil on each side of the mirrorand then driving the coils with an alternating signal at the desiredsweep frequency. The same technique is also used to move the sweep ofthe beam orthogonal to maintain a parallel raster scan. The presentinvention, however, discloses improved techniques for generating aresonant beam sweep.

SUMMARY OF THE INVENTION

[0010] The issues mentioned above are addressed by the present inventionwhich, according to one embodiment, provides a mirror apparatus suitablefor use as the means of generating a sweeping or scanning beam of lightacross the width of a target medium such as the projection screen of adisplay device or a photosensitive medium of a copier. According to oneembodiment, the apparatus comprises a mirror device including areflective surface portion positioned to intercept a beam of light froma light source. The reflective surface of the mirror device is supportedby a first torsional hinge arrangement for pivoting around a first axisand is also supported on a gimbals frame by a second hinge arrangementfor pivoting about a second axis substantially orthogonal to the firstaxis. Thus, pivoting of the mirror device about the first axis resultsin a beam of light reflected from the reflective surface scanning alongthe first dimension of the display screen or photosensitive medium andpivoting of the device about the second axis results in the reflectivelight beam moving in a direction which is substantially orthogonal tothe first direction. The mirror apparatus also includes an inertiallycoupled first driver circuitry for causing resonant pivoting about thefirst axis to provide the repetitive beam sweep or scanning. Suitableinertially coupled drive circuits include electrostatic driver circuitsand piezoelectric drive circuits. There is also included a second drivefor pivoting the mirror about the second axis, such as for example anelectromagnetic drive circuit, such that sequential images or traces arespaced from each other. According to an alternate embodiment, a firstsingle axis mirror is driven by an inertially coupled driver circuit togenerate a resonant beam sweep and a second single axis mirror usestypical electromagnetic drive coils for controlling the orthogonalposition of the resonant beam sweep.

[0011] The foregoing has outlined rather broadly the features andtechnical advantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures or processes for carrying outthe same purposes of the present invention. It should also be realizedby those skilled in the art that such equivalent constructions do notdepart from the spirit and scope of the invention as set forth in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] For a more complete understanding of the present invention, andthe advantages thereof, reference is now made to the followingdescriptions taken in conjunction with the accompanying drawing, inwhich:

[0013]FIG. 1 illustrates an example of a single axis resonant mirrorhaving a support frame for generating a beam sweep, and FIG. 1A is asimplified cross-sectional view taken along lines AA of FIG. 1;

[0014]FIG. 2A is a top view of an alternate embodiment of a single axistorsional hinge mirror supported by a pair of hinge anchors rather thana support frame;

[0015]FIG. 2B is an illustration of an actual device of a single axisflat oval shaped mirror suitable for use with the present invention;

[0016]FIG. 3 is a perspective illustration of the use of twosynchronized single axis mirrors such as shown in FIGS. 1, 2A and 2B togenerate the bi-directional resonant beam sweep across a display screenor a moving photosensitive medium according to the teachings of anembodiment of the present invention;

[0017]FIG. 3A illustrates one complete resonant beam sweep projectedonto a moving photosensitive medium of a laser copier;

[0018]FIG. 3B illustrates a beam sweep path of a frame of image linesprojected onto a display screen;

[0019]FIGS. 4A and 4B, 5A and 5B, 6A and 6B illustrate differentarrangements for using inertially coupled electrostatic drive circuitryto generate the resonant scanning or pivoting about the torsional axisof a single axis mirror;

[0020]FIG. 7 illustrates the electrical connection between theelectrostatic plates and the mirror assemblies of FIGS. 4A and 4B, 5Aand 5B and 6A and 6B;

[0021]FIGS. 8A and 8B, 9A and 9B and 10A and 10B illustrate differentarrangements for using piezoelectric drive circuit to generate theinertially coupled resonant scanning or pivoting about the first orresonant axis of a mirror;

[0022]FIG. 11 illustrates the electrical connection between thepiezoelectric drive material and the mirror assemblies of FIGS. 8A and8B, 9A and 9B, and 10A and 10B;

[0023]FIGS. 12 and 12A are perspective views of two embodiments of atwo-axis torsional hinge mirror having a support frame for generatingthe bi-directional beam sweep according to the teachings of oneembodiment of the present invention;

[0024]FIG. 13 is a top view of an alternate embodiment of a two-axistorsional hinge mirror supported by “hinge anchors” rather than asupport frame;

[0025] FIGS. 14A-14D are cross-sectional views of the mirror of FIG. 12illustrating rotation or pivoting of the two sets of torsional hinges;

[0026]FIGS. 15A, 15B and 15C illustrate the use of a two-axis resonantmirror such as shown in FIGS. 11 and 12 to generate a bi-directionalbeam sweep across a display screen or a moving photosensitive mediumaccording to teachings of the present invention;

[0027]FIG. 16 is a perspective view illustrating the pattern of thebi-directional beam sweep and the resulting parallel beam images as mayappear on a moving photosensitive medium or display screen;

[0028]FIGS. 17A and 17B are top and side views, respectively,illustrating electrostatic drive circuitry to generate the resonantscanning or pivoting about a first pair of torsional axis and thelocation of the electromagnetic drive circuitry for providing orthogonalpositioning of the resonant beam sweep for a single dual axis mirrorwith a support frame;

[0029]FIGS. 18A and 18B are top and side views, respectively,illustrating piezoelectric drive circuitry to generate the resonantscanning or pivoting about a first pair of torsional axis and thelocation of the electromagnetic drive circuitry for providing orthogonalpositioning of the resonant beam sweep for a single dual axis mirrorusing hinge anchors; and

[0030]FIG. 19 illustrates the electromagnetic drive circuit for movingthe scanning light beam orthogonal to the raster scan for both theelectrostatic resonant scan embodiment and the piezoelectric resonantscan embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0031] The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

[0032] Like reference numbers in the figures are used herein todesignate like elements throughout the various views of the presentinvention. The figures are not intended to be drawn to scale and in someinstances, for illustrative purposes, the drawings may intentionally notbe to scale. One of ordinary skill in the art will appreciate the manypossible applications and variations of the present invention based onthe following examples of possible embodiments of the present invention.The present invention relates to mirror apparatus with a moveablereflecting surface that has torsional hinges and is particularlysuitable for use to provide the repetitive scans of a laser printer orthe raster scan of a projection display device. The mirror apparatus ofthis invention includes a single two-axis resonant mirror according toone embodiment. A second embodiment uses one single axis resonant mirrorin combination with a second single axis mirror for providing spaced andparallel scan lines. The second single axis mirror continuously adjuststhe “vertical” movement of the beam with respect to the raster scanmovement.

[0033] Referring now to FIG. 1, there is shown a top view of a mirrorapparatus having a single pair of torsional hinges for pivoting around afirst axis 30. As shown, the mirror apparatus of FIG. 1 includes asupport member 32 suitable for mounting to a support structure 34 asshown in FIG. 1A. FIG. 1A is a simplified cross-sectional view takenalong line A-A of FIG. 1. A reflective surface or mirror portion 36 isattached to support member 32 by a pair of torsional hinges 38A and 38B

[0034] As will be discussed in more detail hereinafter, the mirror orreflective surface portion 36 may be made to pivot or oscillate aboutaxis 30 in response to various types of drive circuits. For example, themirror apparatus may be driven to resonance for providing a repetitivebeam sweep by electrostatic or piezoelectric drive circuits, or may bycontrolled much more directly to provide a slower orthogonal or verticalcontrol to index each beam sweep to maintain spacing between successivelines on a projection display while at the same time maintaining all ofthe beam sweeps parallel to each other. Electromagnetic drive circuitryis particularly suitable for the vertical or orthogonal drive. When amirror apparatus is to be used to control the orthogonal or verticalposition of the beam sweep and is driven by an electromagnetic circuit,small magnets are typically included as indicated by dashed line areas40A and 40B located on tabs 42A and 42B. The placement and use of thesmall magnets will be discussed in more detail with respect to FIGS. 14Athrough 14D. The magnets are mounted on the tabs 42A and 42B to avoiddegrading the reflective surface 36.

[0035] Although the mirror apparatus of FIG. 1 includes a support memberor frame 32, reflective surface or mirror portion 36 may be manufacturedby eliminating the support member 32 and extending the torsional hinges38A and 38B from mirror portion 36 to a pair of hinge anchors 44A and44B as shown in FIG. 2A. The hinge anchors are then attached or bondedto the support structure 34 as shown in FIG. 1A. FIG. 2A alsoillustrates that the mirror or reflective surface portion 36 may haveany suitable shape or perimeter such as the hexagon shape indicated bydotted line 46. Other suitable shapes may include oval, square oroctagonal. For example, FIG. 2B illustrates an actual mirror found to besuitable for use in providing the resonant beam sweep. As can be seen,the mirror portion 36A is a very flat oval shape having a long dimensionof about 5.5 millimeters and a short dimension of about 1.2 millimeters.

[0036] Referring to FIG. 3 there is a perspective illustration of anembodiment of the present invention using two mirrors, each of whichpivot about a single axis, such as the single axis mirrors shown inFIGS. 1, 2A and 2B. In addition, although FIGS. 1, 2A and 2B illustratea single axis mirror, two dual axis mirrors of the type shown in FIG. 12and discussed hereinafter, can be used to obtain the same results asachieved by using two single axis mirrors. For example, two of thetwo-axis mirror arrangements shown in FIG. 12 may be used by notproviding (or not activating) the drive mechanism for one of the axes.However, if two mirrors are to be used, it is believed to beadvantageous to use two of the more rugged single axis mirrors such asshown in FIGS. 1, 2A and 2B as discussed above.

[0037] Therefore, referring to FIG. 3, a first single axis analogtorsional hinged mirror may be used in combination with a second similarsingle axis torsional mirror to solve the problems of a resonantscanning mirror type projection display or laser printer. As shown,there is a first mirror apparatus 48 such as discussed above withrespect to FIGS. 1, 2A and 2B that includes a support member 32supporting a mirror or reflective surface 36 by the single pair oftorsional hinges 38A and 38B. Thus, it will be appreciated that if themirror portion 36 can be maintained in a resonant state by a drivesource, the mirror can be used to cause a resonant oscillating lightbeam across a photosensitive medium. However, as will also beappreciated, there also needs to be a method of moving the light beam ina direction orthogonal to the oscillation if line images are to bemaintained parallel. Therefore, as will be discussed with respect toFIG. 3, a second single axis mirror apparatus 50, such as illustrated inFIGS. 1 and 2, may also used to provide the vertical movement of thelight beam.

[0038] The system of the embodiment of FIG. 3 uses the first single axismirror apparatus 48 to provide the right to left, left to right resonantsweep as represented by dotted lines 52A, 52B, 52N-l and 52N. However,the up and down control of the beam trajectory is achieved by locatingthe second single axis mirror apparatus 50 such that the reflectivesurface or mirror portion 36A intercepts the light beam 54 emitted fromlight source 56 and then reflects the intercepted light to the mirrorapparatus 48 which is providing the resonant sweep motion. Line 58 shownon mirror surface 36 of resonant mirror 48 illustrates how mirror 36Arotates around axis 60 to move the light beam 54A up and down onreflective surface 36 of mirror apparatus 48 during the left to rightand right to left beam sweep so as to provide parallel lines 52A, 52Bthrough 52N-1 and 52N on a projection display screen or a moving medium62. Double headed arrow 64 illustrates the vertical or orthogonalmovement of the beam sweep projected from mirror surface 36 of mirrorapparatus 48.

[0039] Referring now to FIGS. 3A and 3B, there is shown an exaggeratedschematic of the light beam trajectory responsive to movement about twoaxes during a complete resonant cycle of mirror apparatus 48. Asdiscussed above, the movement about two axes may be provided by twosingle axis mirrors as illustrated in FIG. 3 or a single dual axismirror to be discussed later. The beam trajectory illustrated in FIG. 3Ais shown with a photosensitive medium 66 moving as indicated by arrow 68to illustrate how the beam trajectory generates parallel image lines fora laser copier during successive scan lines of a single resonant cycle.In the example shown in FIG. 3A, a right to left movement portion of thebeam trajectory is identified by the reference number 70. It should beunderstood that the term “beam trajectory” as used herein does notnecessarily mean that the laser light is on or actually providing light.The term is used herein to illustrate the path that would be traced ifthe light was actually on at all times. As will be appreciated by thoseskilled in the art, the light source is typically turned on and offcontinuously due to modulation and is also typically switched off at thetwo ends (left and right) of a scan or sweep. However, the modulationpattern can vary from being on for the complete scan or sweep to beingoff for the complete scan. Modulation of the scanning beam, andswitching off at the end portion of a scan is also, of course, true forall types of laser printers including laser printers which use arotating polygon mirror. Therefore, in the embodiment shown in FIG. 3A,the laser beam is capable of providing modulated light at about point 72which is next to edge 74 of medium 66. However, as will be recognized, aprinted page usually includes left and right margins. Therefore,although a printed image line could begin at point 72 on a right to leftscan of the beam trajectory as shown by trajectory portion 70, themodulated light beam does not actually start to produce an image untilpoint 76 at margin 78 of the right to left portion of the trajectory andstops printing at the left margin 80. This is also indicated at therightmost dot 82 on the printed image line 84. It is important to againpoint out that for a laser printer application the photosensitive medium66 is moving in a direction as indicated by arrow 68. Therefore, togenerate the top printed image line 84 between margins 78 and 80 as ahorizontal line, the right to left beam trajectory is orthogonallycontrolled by mirror assembly 50 pivoting on torsional hinges 86A and86B about axis 30A an appropriate amount so that the resulting linebetween the beginning right end point 72 and the left ending point 82 ishorizontal. That is, the beam trajectory is moved up during a beam sweepby substantially the same amount or distance as the constantly movingphotosensitive medium 66 moves up during the right to left beam sweep.After the right to left portion of the beam trajectory is complete atthe left edge 88 of medium 66 (i.e., half of the resonant cycle), themirror is pivoted about torsional hinges 86A and 86B in the oppositedirection as the resonant mirror 36 changes the direction of its sweepas indicated by portion 90 of the beam trajectory. Then, when the leftto right portion 92 of the trajectory beam sweep (resulting frompivoting about axis 30 on torsional hinges 38A and 38B or mirrorapparatus 48) again reaches the left edge 80 of medium 66, the mirror isagain pivoted about torsional hinges 86A and 86B to move the left toright portion 92 of the beam trajectory upward as it traverses medium 66in a manner similar to the right to left portion of the trajectory.Thus, the line of image 94 starting at beginning point 96 and generatedduring the left to right scan is maintained parallel to the previousgenerated image line 84. Then as the beam trajectory passes the rightedge 74 of the medium 66, the resonant scan mirror apparatus 48 againbegins to reverse its direction by pivoting in the opposite directionabout torsional hinges 38A and 38B so as to return to the starting point72. The cycle is then of course repeated for another complete resonantsweep such that two more image lines are produced.

[0040]FIG. 3B illustrates a similar beam pattern projected onto adisplay screen having an orthogonal dimension rather than onto themoving medium of a laser printer. As shown in FIG. 3B, the movement ofthe beam is the same as discussed with respect to FIG. 3A with respectto portions 70 through 92 of the beam sweep. However, after the beamtrajectory passes the right edge 78 of the display screen 66A and beginsto reverse its direction by pivoting in the opposite direction abouthinges 38A and 38B, instead of returning to point 72 an orthogonalincremental increase is added to index the trajectory, as indicated at98, the equivalent of one scan line so that the beginning point is nowat 72A rather than 72. The resonant cycle then continues as before,except it is orthogonally incremented at the end of every cycle to a newstarting point as indicated at points 72B 72C, etc. Once the trajectoryhas been incremented an amount equal to the full vertical display (i.e.,completed a full display frame), the starting point is againrepositioned at 72 as indicated by return line 100 and the full rasterscan of a new frame begins.

[0041] Referring now to FIGS. 4A and 4B, 5A and 5B and 6A and 6B, thereare shown top views and side views, respectively, for driving a singleaxis torsional hinge mirror, such as mirror 36 of FIG. 3, intoresonance. As shown, according to these embodiments, the mirrorapparatus 102 includes a support frame 104 having two long sides 106Aand 106B and two short sides 108A and 108B. The two long sides 106A and106B are mounted or bonded to a support structure 110 by an adhesive orepoxy by means of stand-offs 112A and 112B. Also as shown in the sideview of FIG. 4B, support structure 110 defines a cavity 114. A mirror orreflective surface portion 116 is attached to the two short sides 108Aand 108B by a pair of torsional hinges 118A and 118B such that themirror or reflective surface portion 116 is located above the cavity114. As is clearly shown, the perimeter of cavity 114 is larger than theperimeter of reflective surface or mirror portion 116 such that mirror116 can freely rotate around torsional hinges 118A and 118B withouthitting the bottom of cavity 114.

[0042] As mentioned above, electromagnetic drives have been successfullyused to rotate torsional hinged supported mirror 116 about the axis 120through hinges 118A and 118B. Such electromagnetic drives may be used toset up resonance oscillation of the mirror 116 about its axis in amanner as will be discussed below, but are more useful for controllingthe position of a second mirror such as mirror 36A for orthogonallypositioning the resonant beam sweep in response to varying signalsprovided by computational circuitry to be discussed later. Furthermore,such electromagnetic drives require the mounting of electromagneticcoils below the mirror thereby adding cost and taking up space.According to one embodiment of the present invention, mirror 116 iscaused to resonant about the axis 120 by electrostatic forces.Therefore, referring again to the embodiment of FIGS. 4A and 4B, thereis included a pair of electrostatic drive plates 122A and 122B locatedbelow the short sides 108A and 108B of support frame 104. Also as shownin the side view of FIG. 4B, stand-off mounting members 112A and 112Bare selected such that a gap 124A and 124B exists between the bottomsurface of short sides 108A and 108B and the top surface ofelectrostatic drive plates 122A and 122B. It has been determined thatselecting the thickness of the stand-off mounting 112A and 112B suchthat gaps 124A and 124B are between about 0.2 μm and 0.05 μm isparticularly effective. An alternating voltage is then connected betweenthe mirror support structure 104 and the electrostatic plates 122A and122B.

[0043] As an example, and assuming the mirror is designed to have aresonant frequency about its torsional hinges that is no less than about40 KHz when used as the scanning mirror of a display device, and betweenabout 1 KHz and 4 KHz when used as the scanning mirror for a printer, ifan alternating voltage also having a frequency substantially equivalentto the resonant frequency is connected across the electrostatic platesand the support frame 104, the mirror will begin to oscillate atsubstantially the frequency of the applied voltage. The actual resonantfrequency of a mirror can be determined by maintaining the voltage levelconstant and varying the frequency of the applied voltage between thetwo voltage limits. A frequency in which the mirror rotation is maximum,will be the resonant frequency. The oscillations of the mirror resultsfrom the vibrational forces generated by the “on/off” electrostaticforces between the mirror support frame 104 and the electrostatic plates122A and 122B being inertially coupled to the mirror 116 through thetorsional hinges 118A and 118B. The resonant frequency of the mirrorvaries not only according to the size of the mirror itself, but alsoaccording to the length, width and thickness of the two torsional hinges118A and 118B. It should be noted that in the embodiment of FIG. 4A, thetorsional hinges 118A and 118B are not attached to the midpoint of sidesof mirror portion 116. That is, the axis 120 lying through the torsionalhinges 118A and 118B does not divide the mirror portion 116 into twoequal parts. As shown, the “bottom” portion of the illustration ofmirror 116 is larger than the “top” portion. It will be appreciated, ofcourse, that use of the terms “bottom” portion and “top” portion is forconvenience in describing the device and has nothing to do with theactual positioning of the device. Although attaching the hinges “offcenter” may help initiate resonance in the structure by creating animbalance, it has been determined that resonance of the mirror may beachieved almost as quickly if the mirror is not off center. Furthermore,stresses may well be reduced and the required energy to maintainresonance may be somewhat less with a balanced arrangement.

[0044] Referring now to FIGS. 5A and 5B, there is a top view and a sideview, respectively, of an alternate embodiment for resonating reflectiveportion 116 of the mirror apparatus 102. The components of the mirrorstructure of FIGS. 5A and 5B are substantially the same as those forFIGS. 4A and 4B discussed above. However, rather than mounting thesupport frame 104 to the support structure 110 at the center point ofboth long side 118A and 118B, one of the two short ends such as, forexample, short end 108A is mounted to support structure 110 by a singlelarge stand-off 112C. A single electrostatic plate 122B is then locatedat a very small spaced distance below the other short end 108B in thesame manner as discussed above with respect to FIGS. 4A and 4B. Analternating voltage source is then connected between the mirrorstructure and the electrostatic plate in the same manner as discussedabove. The mirror support frame 104 will again vibrate in response tothe on/off electrostatic attraction and the energy in turn is inertiallycoupled to the reflective portion 116 which begins oscillating abouttorsional hinges 118A and 118B in the same manner as discussed above.

[0045] Still another embodiment is illustrated in top and side viewsFIG. 6A and FIG. 6B respectively. According to this embodiment,torsional hinges 118A and 118B do not extend from the reflective surfaceportion 116 to a support frame, but instead extend to enlarged anchormembers 126A and 126B. End portions 128A and 128B of the anchors 126Aand 126B are located or mounted to the support structure 110 bystand-offs 112D and 112E such that the opposite end portions 130A and130B of each anchor are suspended or spaced above electrostatic plates132A and 132B by a small gap. Thus, in the same manner as discussedabove, an alternating voltage having a frequency substantially the sameas the resonant frequency of the mirror 116 about is axis can beconnected between the support anchors 126A and 126B and theelectrostatic plates 132A and 132B to cause the mirror 116 to resonantand oscillate around the torsional hinges.

[0046]FIG. 7 is applicable to FIGS. 4A and 4B, 5A and 5B and 6A and 6Band illustrates the electrical connections 133A and 133B for applying analternating voltage between the mirror structure and the electrostaticplates.

[0047]FIGS. 8A and 8B, FIGS. 9A and 9B, and FIGS. 10A and 10B illustrateresonant mirror arrangements mounted to the support structure in thesame manner as discussed above with respect to FIGS. 4A and 4B, FIGS. 5Aand 5B and FIGS. 6A and 6B respectively. However, rather than usingelectrostatic plates and electrostatic forces to generate resonantmotion of the mirror around its torsional axis, these three embodimentsemploy slices of piezoelectric material 134A, 134B, 134C and/or 134Dbonded to the support frame 104 and/or anchors 130A and 130B. Thepiezoelectric material 134A-134D is sliced such that it bends or curveswhen a voltage is applied across the length of the strip or slice ofmaterial. As will be understood by those skilled in the art, theresponse time for piezoelectric material will be very fast such that analternating voltage will cause a strip of the material to bend and curveat the same frequency as the applied voltage. Therefore, since thematerial is bonded to the support frame 104 or support anchors, 130Aand/or 130B, the application of an alternating voltage having afrequency substantially equal to the resonance frequency of the mirror,will cause the vibration motion to be inertially coupled to thereflective portion 116 and to thereby initiate and maintain the resonantoscillation as discussed above.

[0048]FIG. 11 illustrates the electrical connections for providing analternating voltage to the mirror structure and the two ends ofpiezoelectric materials.

[0049] Therefore, it will be appreciated that the single axis mirrorstructure discussed above with respect to FIGS. 4A through 10B may beused as the mirror structure 48 of FIG. 3 to provide the resonant sweepof the two single axis mirror arrangement discussed heretofore withrespect to FIG. 3. Movement of the second mirror 50 in the arrangementof FIG. 3 may be directly controlled to provide the necessary orthogonalmovement by electromagnetic coils as also discussed above.

[0050] Referring now to FIG. 12, there is shown a perspective view of asingle two-axis bi-directional mirror assembly 140 which can be used toprovide resonant scanning or beam sweeps across a projection displayscreen or moving photosensitive medium as well as adjusting the beamsweep in a direction orthogonal to the resonant oscillations of thereflective surface or mirror portion 142 to maintain spaced parallelimage lines produced by the resonant raster beam sweep. As shown, mirrorassembly 140 is illustrated as being mounted on a support structure 144.The mirror assembly 140 may be formed from a single piece ofsubstantially planar material and the functional or moving parts may beetched in the planar sheet of material (such as silicon) by techniquessimilar to those used in semiconductor art. As discussed below, thefunctional or moving components include, for example, the frame portion146, an intermediate gimbals portion 148 and the inner mirror portion142. It will be appreciated that the intermediate gimbals portion 148 ishinged to the frame portion 146 at two ends by a first pair of torsionalhinges 150A and 150B spaced apart and aligned along a first axis 152.Except for the first pair of hinges 150A and 150B, the intermediategimbals portion 148 is separated from the frame portion 146.

[0051] The inner, centrally disposed mirror portion 142 having areflective surface centrally located thereon is attached to gimbalsportion 148 at hinges 154A and 154B along a second axis 156 that isorthogonal to or rotated 90° from the first axis. The reflective surfaceon mirror portion 142 is on the order of about 100-115 microns inthickness and is suitably polished on its upper surface to provide aspecular or mirror surface. In order to provide necessary flatness, themirror is formed with a radius of curvature greater than approximately 2meters with increasing optical path lengths requiring increasing radiusof curvature. The radius of curvature can be controlled by known stresscontrol techniques such as by polishing on both opposite faces anddeposition techniques for stress controlled thin films. If desired, acoating of suitable material can be placed on the mirror portion toenhance its reflectivity for specific radiation wavelengths.

[0052]FIG. 12A is an alternate embodiment of a dual axis mirrorapparatus having an elongated oval mirror portion 142A. Since theremaining elements of the mirror apparatus shown in FIG. 12A operate orfunction in the same manner as equivalent elements of FIG. 12, the twofigures use common reference numbers.

[0053] Referring now to FIG. 13, there is shown another alternateembodiment of a dual axis mirror. In this embodiment, the outsidesupport frame has been eliminated such that the torsional hinges 150Aand 150B extend from the gimbals frame or portion 148 to hinge anchors158A and 158B. Hinge anchors 158A and 158B are of course used to mountor attach the mirror to a support structure such as discussed withrespect to FIG. 12. It should also be appreciated that the operation ofthe dual torsional hinged mirror of FIG. 13 operates the same as thedual torsional hinged mirror discussed with respect to FIGS. 12 and 12A.

[0054] Referring to FIGS. 14, 14B, 14C and 14D along with any one of themirrors illustrated in FIGS. 12, 12A and 13, the motion of the dual axismirror will be explained. Mirror assembly 140 will be discussed withrespect to inertially coupled driver circuits similar to those discussedabove to generate the resonant scanning or beam sweep movement of themirror 142 about axis 156 illustrated in FIGS. 14A and 14B. The use ofsuch inertially coupled resonance with a single dual axis mirror will bediscussed in detail hereinafter. FIGS. 14A and 14B represent across-section of the dual axis mirror of FIG. 12 taken along lines12A-12A (on axis 152), and FIGS. 14C and 14D are cross-sections of FIG.12 taken along lines 12B-12B (on axis 156).

[0055] Whereas the oscillating motion of the reflective surface 142 isprovided by resonant drive circuits, motion of the gimbals portion 148about axis 152 on the other hand, is provided by another type of drivercircuits such as, for example, serially connected electromagnetic coils160A and 160B, which are connected to computational or control circuitryfor providing a control signal to provide a pair of electromagneticforces for attracting and repelling the gimbals portion 148. The gimbalsportion 148 may also include a first pair of permanent magnets 162A and162B mounted on gimbals portion 148 along the axis 156 to enhance theoperation of the electromagnetic coils. In order to symmetricallydistribute mass about the two axes of rotation to thereby minimizeoscillation under shock and vibration, each permanent magnet 160A and160B preferably comprises an upper magnet set mounted on the top surfaceof the gimbals portion 148 using conventional attachment techniques suchas indium bonding and an aligned lower magnet similarly attached to thelower surface of the gimbals portion 148 as shown in FIGS. 14A through14D. The magnets of each set are arranged serially such as thenorth/south pole arrangement indicated in FIG. 14C. There are severalpossible arrangements of the four sets of magnets which may be used,such as all like poles up; or two sets of like poles up, two sets oflike poles down; or three sets of like poles up, one set of like polesdown, depending upon magnetic characteristics desired.

[0056] As will be discussed, pivoting about axis 152 as shown in FIGS.14C and 14D will provide the orthogonal scanning (or vertical) motionnecessary to generate a series of spaced image lines parallel to eachother. Thus, by mounting reflective surface or mirror portion 142 ontoto gimbals portion 148 via hinges 154A and 154B, resonant motion of themirror portion relative to the gimbals portion occurs about axis 156 andthe orthogonal sweep or motion occurs about axis 152.

[0057] The middle or neutral position of mirror portion 142 is shown inFIG. 14A which is a section taken through the assembly along line12A-12A (or axis 152) of FIG. 12. Rotation of mirror portion 142 aboutaxis 156 independent of gimbals portion 148 and/or frame portion 146 isshown in FIG. 14B as indicated by arrow 162. FIG. 14C shows the middleposition of the mirror assembly 140, similar to that shown in FIG. 14A,but taken along line 12C-12C (or axis 156) of FIG. 12. Rotation of thegimbals portion 148 (which supports mirror portion 142) about axis 152independent of frame portion 146 is shown in FIG. 14D as indicated byarrow 164. The above arrangement allows independent rotation of mirrorportion 142 about the two axes which in turn provides the ability todirect the scanning or raster movement of the light beam about axis 156and the orthogonal sweep or movement about axis 152.

[0058]FIGS. 15A, 15B and 15C illustrate the use of a dual orthogonalscanning resonant mirror according to one embodiment of the presentinvention for providing parallel image lines on a moving photosensitivemedium such as a drum 166 rotating around axis 168. The uppermostportions of FIGS. 15A, 15B and 15C are simplified top views of a dualaxis mirror for providing a beam sweep on medium or rotating drum 166.The lowermost portion of the figure is a view looking at the medium 166in a direction as indicated by arrow 170. As can be seen from FIGS. 15Aand 15B, the operation of dual orthogonal scanning mirror assembly 140as it scans from right to left in the figures is substantially the sameas a single axis mirror in that it is not necessary to provideorthogonal motion if the mirror is mounted at a slight angle. Forexample, point 76 on FIG. 15A illustrates the starting point forproducing an image line or rotating drum 166 and FIG. 15B illustratesthe path of the beam illustrated by line 70 to produce an image line 84which is at a right angle to the movement of drum 166. However, unlike asingle axis resonant mirror and as shown in FIG. 15C, it is notnecessary to turn off the laser (light beam) on the return scan, since areturn or left to right scan 92 in FIGS. 15A, 15B and 15C can becontinuously modulated so as to produce a printed image line 94 on themoving photosensitive medium 166. The second printed line of images 94,according to the present invention, will be parallel to the previouslyproduced line of images 84 generated by the right to left scan 70 of thelight beam. This is, of course, accomplished by slight pivoting of themirror around the secondary axis 152 of the dual axis mirror as wasdiscussed above.

[0059] The operation of the dual axis mirror with respect to aprojection display screen 164 may be better understood by referring toFIG. 16. As shown, a laser light source 56 provides a coherent beam oflight 54 to the reflective surface of mirror portion 142 of dual axismirror apparatus 140 which in turn reflects the beam of light onto adisplay screen 62. Reflective surface 142 is oscillating back and forthat a resonant frequency about torsional hinges 154A and 154B along axis156 and thereby sweeps the beam across display screen 62 along imageline 84 from location or point 72 to end point 82 as indicated by arrow172 in the light beam labeled 54A-2. The oscillating mirror 142 thenchanges direction and at the same time the beam is moved or incrementedorthogonally as indicated at path 174 to point 176 and starts the returnsweep as indicated by arrow 178 to produce image line 94 between points176 and 180. After passing point 180, the beam again begins reversingdirection and is again incremented to a new start point 182 to beginanother back and forth sweep. This process is repeated until the lastimage line 94N of a display frame ending at point 184 is produced ondisplay screen 62. The beam is then orthogonally moved from end point184 to start point 72 as indicated by dashed line 186 to start a newdisplay frame. As mentioned above, mirror portion 142 is made toresonate to produce the repetitive beam sweep.

[0060] Referring now to FIGS. 17A and 17B, there is a simplified topview and side view of the mirror apparatus for generating both theresonant frequency sweeping movement and the orthogonal movement forbeam positioning. In a manner discussed above with respect to FIGS. 4Athrough 6A, a support frame 146 is mounted on a support structure 144above a cavity 188 such that both mirror portion 142 and gimbals portion148 can rotate about their respective axes 156 and 152. Support frame146 is mounted at its long sides 190A and 190B on mounts or spacingmembers 192A and 192B such that the short ends 194A and 194B are spacedabove electrostatic drive plates 196A and 196B by a small gap on theorder of between about 0.2 μm and 0.05 μm. An alternating drive voltagehaving a frequency which is approximately the resonant frequency of themirror portion 142 about its hinges, is then applied between theelectrostatic drive plates and the mirror supporting frame 146 togenerate vibrations in the mirror apparatus as was discussed above withrespect to a single axis mirror and as was illustrated in FIG. 7. Theenergy of the vibration is inertially coupled through torsional hinges150A and 150B to gimbals portion 148 and then through mirror hinges 154Aand 154B to the mirror portion 142. This energy vibration atapproximately the resonant frequency of the mirror causes the mirrorportion 142 to begin resonant oscillations about hinges 154A and 154Balong axis 156 and can be used to provide the resonant beam sweep asdiscussed above. The orthogonal motion is controlled by electromagneticcoils 198A and 198B as shown in FIG. 17B and FIG. 19. As discussedabove, permanent magnet sets 200A and 200B may be bonded to the gimbalsportion 148 to provide better stability and performance of theorthogonal drive. It should also be understood that although the energyinertially coupled to mirror portion 142 sets the mirror oscillating ata full sweep and at a resonant frequency, the motion of the gimbalsframe due to energy from the electrostatic plate is very slight suchthat the orthogonal movement can still be precisely controlled.

[0061] In a similar manner as discussed above with respect to singleaxis mirrors, the dual axis mirror can also be driven to resonance by apiezoelectric drive circuit. For example, as shown in FIGS. 18A and 18B,support frame 146 is mounted to support structure 144 by mounts 192A and192B as discussed above with respect to FIGS. 17A and 17B. However,instead of electrostatic plates, slices of piezoelectric material 202A,202B, 202C and 202D are bonded to the support frame 146. An alternatingvoltage having a frequency approximately the resonant frequency ofmirror portion 142 about torsional axis 154A and 154B is applied betweenboth ends of the slices of piezoelectric material as discussed abovewith respect to FIG. 11. In the same manner as discussed with respect toFIGS. 17A and 17B, vibrating energy of the mirror resonant frequency isinertially coupled from the frame to the mirror portion 142 so as to putthe mirror into resonant oscillation. The resonant oscillation can thenbe used to provide the resonant beam sweep for a projection display orlaser copier and an electromagnetic drive circuitry can be used toprovide the necessary orthogonal motion.

[0062] The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed as many modifications andvariations are possible in light of the above teaching. The embodimentswere chosen and described in order to best explain the principles of theinvention and its practical application to thereby enable others skilledin the art to best utilize the invention and various embodiments withvarious modifications as are suited to the particular use contemplated.It is intended that the scope of the invention be defined by the claimsappended hereto and their equivalents.

[0063] Although the present invention and its advantages have beendescribed in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the invention as defined by the appended claims.

[0064] Moreover, the scope of the present application is not intended tobe limited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

What is claimed is:
 1. Apparatus for providing a resonant beam sweepabout a first axis, said apparatus comprising: a mirror deviceintegrally formed from a single piece of material comprising areflective surface portion positioned to intercept a beam of light froma light source, and a first pair of torsional hinges attached to saidreflective surface portion and extending to a support portion forpivoting said reflective surface portion about said first axis; and adriver circuit for generating vibrational energy in said support portionand wherein said vibrational energy is inertially coupled from saidsupport portion through said first pair of torsional hinges to saidreflective surface portion such that said reflective surface portionoscillates about said first pair of torsional hinges between a selectedlower limit below a resonant frequency and a selected upper limit abovesaid resonant frequency.
 2. The apparatus of claim 1 further comprisinga support structure and wherein said support portion of said mirrordevice is a frame member having a first portion thereof attached to saidsupport structure.
 3. The apparatus of claim 1 wherein said supportportion comprises first and second support anchors attached to a supportstructure.
 4. The mirror device of claim 1 wherein said driver circuitcomprises at least one electrostatic plate spaced a selected distancefrom said support portion and an alternating voltage source connectedbetween said at least one electrostatic plate and said support portionand wherein the frequency of said alternating voltage source is betweensaid selected lower limit and said selected upper limit.
 5. Theapparatus of claim 1 wherein said driver circuit comprises at least oneportion of piezoelectric material having a first end and a second end,said portion of piezoelectric material bonded to said support portionand an alternating voltage source connected between said first end andsaid second end of said portion of piezoelectric material, and whereinthe frequency of said alternating voltage source is between saidselected lower limit and said selected upper limit.
 6. The apparatus ofclaim 1 wherein said driver circuit comprises a pair of electromagneticcoils, one each of said pair located on each side of said first axis andspaced from said reflective surface portion, and an alternating voltagesource connected across said pair of coils, and wherein the frequency ofsaid alternating voltage source is between said selected lower limit andsaid selected upper limit.
 7. The apparatus of claim 1 wherein saidsupport portion of said mirror device comprises a support frame and agimbals portion supported by a second pair of torsional hinges locatedat substantially a right angle with said first pair of hinges andextending to said support frame, said gimbals portion pivoting about asecond axis orthogonal to said first axis.
 8. The apparatus of claim 7wherein said driver circuit comprises at least one electrostatic platespaced a selected distance from said support frame and an alternatingvoltage source connected between said at least one electrostatic plateand said support frame and wherein the frequency of said alternatingvoltage source is between said selected lower limit and said selectedupper limit.
 9. The apparatus of claim 7 wherein said driver circuitcomprises at least one portion of piezoelectric material having a firstend and a second end, said portion of piezoelectric material bonded tosaid support frame and an alternating voltage source connected betweensaid first end and said second end of said portion of piezoelectricmaterial, and wherein the frequency of said alternating voltage sourceis between said selected lower limit and said selected upper limit. 10.The apparatus of claim 7 wherein said driver circuit comprises a pair ofelectromagnetic coils, one each of said pair located on each side ofsaid first axis and spaced from said reflective surface portion, and analternating voltage source connected across said pair of coils, saidfrequency of said alternating voltage source selected to be between saidselected lower limit and said selected upper limit.
 11. The apparatus ofclaim 8, and further comprising a pair of electromagnetic coils, oneeach of said pair located on each side of said second axis and spacedfrom said gimbals portion, and a voltage source connected across saidpair of coils for selectively positioning said resonant beam sweep in adirection orthogonal to said beam sweep.
 12. The apparatus of claim 9,and further comprising a pair of electromagnetic coils, one each of saidpair located on each side of said second axis and spaced from saidgimbals portion, and a voltage source connected across said pair ofcoils for selectively positioning said resonant beam sweep in adirection orthogonal to said beam sweep.
 13. The apparatus of claim 10,and further comprising a second pair of electromagnetic coils, one eachof said second pair located on each side of said second axis and spacedfrom said gimbals portion, and voltage source connected across saidsecond pair of coils for selectively positioning said resonant beamsweep in a direction orthogonal to said beam sweep.
 14. The apparatus ofclaim 1 wherein said support portion of said mirror device comprises agimbals portion supported by a second pair of torsional hinges locatedat substantially right angles with said first pair of hinges and saidsecond pair of torsional hinges extending one each to one of a pair ofsupport anchors, said second pair of torsional hinges for pivoting abouta second axis orthogonal to said first axis.
 15. The apparatus of claim14 wherein said driver circuit comprises at least one electrostaticplate spaced a selected distance from at least one of said pair ofsupport anchors and an alternating voltage source connected between saidat least one electrostatic plate and at least one of said pair ofsupport anchors and wherein the frequency of said alternating voltagesource is between said selected lower limit and said selected upperlimit.
 16. The apparatus of claim 14 wherein said driver circuitcomprises at least one portion of piezoelectric material having a firstend and a second end, said portion of piezoelectric material bonded toat least one of said pair of support anchors and an alternating voltagesource connected between said first end and said second end of saidportion of piezoelectric material, and wherein the frequency of saidalternating voltage source is between said selected lower limit and saidselected upper limit.
 17. The apparatus of claim 14 wherein said drivercircuit comprises a pair of electromagnetic coils, one end of said pairlocated on each side of said first axis and spaced from said reflectivesurface portion, and an alternating voltage source connected across saidpair of coils and wherein the frequency of said alternating voltagesource is between said selected lower limit and said selected upperlimit.
 18. The apparatus of claim 15, and further comprising a pair ofelectromagnetic coils, one each of said pair located on each side ofsaid second axis and spaced from said gimbals portion, and a voltagesource connected across said pair of coils for selectively positioningsaid resonant beam sweep in an orthogonal direction with respect to saidbeam sweep.
 19. The apparatus of claim 16, and further comprising a pairof electromagnetic coils, one each of said pair located on each side ofsaid second axis and spaced from said gimbals portion, and voltagesource connected across said pair of coils for selectively positioningsaid resonant beam sweep in an orthogonal direction with respect to saidbeam sweep.
 20. The apparatus of claim 17, and further comprising asecond pair of electromagnetic coils, one each of said second pairlocated on each side of said second axis and spaced from said gimbalsportion, and voltage source connected across said second pair of coilsfor selectively positioning said resonant beam sweep in an orthogonaldirection with respect to said beam sweep.
 21. Apparatus for providing arepetitive beam sweep, comprising: a light source for providing a beamof light; an integrally formed mirror device comprising a reflectivesurface portion positioned to intercept a beam of light, a first pair oftorsional hinges and a gimbals portion pivotally attached to saidreflective surface portion by said first pair of torsional hinges, asupport member and a second pair of torsional hinges, said second pairof torsional hinges extending between said support member and saidgimbals portion such that pivoting of said device about said first pairof torsional hinges results in said light beam reflected from saidreflective surface defining a first plane and pivoting of said deviceabout said second pair of torsional hinges results in said reflectivelight moving in a direction substantially orthogonal to said first path;a first driver for generating vibrational energy in said support memberof said mirror device and wherein said vibrational energy is inertiallycoupled through said second pair of torsional hinges to said gimbalsportion and from said gimbals portion through said first pair oftorsional hinges to said reflective surface portion for causing resonantpivoting in one direction about said first pair of said torsional hingesand then the opposite direction such that said reflected light beamsweeps or traces across a target area having a first dimension and asecond dimension that is orthogonal to said first dimension, saidreflected light beam sweeping along said first dimension of said targetarea as said mirror device pivots about said first pair of torsionalhinges; and a second driver for pivoting said mirror device about saidsecond pair of torsional hinges such that consecutive beam sweeps acrosssaid target are repositioned substantially orthogonal with respect tosaid beam sweep.
 22. The mirror device of claim 21 wherein said targetarea is a rotating cylindrical shaped photosensitive medium.
 23. Themirror device of claim 21 wherein said target area is a display screen.24. A printer comprising: a light source providing a beam of light; afirst integrally formed device comprising a reflective surface portionpositioned to intercept said beam of light, a support portion, and afirst pair of torsional hinges attached to said reflective surfaceportion and extending to said support portion for resonant pivotingabout a first axis such that light reflected from said reflectivesurface defines a first path; a first drive circuit for generatingvibrational energy in said support portion, said vibrational energyinertially coupled through said first pair of torsional hinges to saidreflective surface portion to cause resonant pivoting of said firstdevice about said first axis to provide a resonant beam sweep; a seconddevice for rotating about a second axis such that light from saidreflective surface moves in a second direction substantially orthogonalto said first path; a moving photosensitive medium having a firstdimension and a second dimension orthogonal to said first dimension, andlocated to receive an image of said reflected light beam as said beamsweeps across said medium along said first dimension, saidphotosensitive medium moving in a direction along said second dimensionsuch that subsequent traces are spaced apart; and a second drive circuitfor rotating said second device about said second axis such that tracesare received on said moving photosensitive medium along a linesubstantially orthogonal to the movement of said photosensitive medium.25. The printer of claim 24 wherein said first and second devicestogether comprise an integrally formed single dual axis mirror andwherein said support portion is a gimbals support pivotally attached toa support member by a second pair of torsional hinges and wherein saidmirror of said first device is attached to said gimbals support by saidfirst pair of torsional hinges.
 26. The printer of claim 24 wherein saidfirst device comprises a first single axis torsional hinged mirror andsaid second device comprises a second single axis torsional hingedmirror, said second device positioned to intercept said beam of lightfrom said light source and reflect said light beam to said reflectivesurface of said first device.
 27. The printer of claim 24 wherein saidmoving photosensitive medium is cylindrical shaped and rotates about anaxis through the center of said cylinder.
 28. A printer comprising: alight source providing a beam of light; an integrally formed mirrordevice comprising a reflective surface portion positioned to interceptsaid beam of light from said light source, a first hinge arrangement forsupporting said reflective surface and for pivoting about a first axis,a gimbals portion and a second hinge arrangement, said gimbals portionattached to said first hinge arrangement and supported by said secondhinge arrangement for pivoting about a second axis substantiallyorthogonal to said first axis such that pivoting of said device aboutsaid first axis results in light reflected from said reflective surfacedefining a first path, and pivoting of said device about said secondaxis results in said reflective light moving in a second directionsubstantially orthogonal to said first path; a first driver forgenerating vibrational energy inertially coupled through said secondhinge arrangement, said gimbals portion and through said first hingearrangement to said reflective surface portion to cause resonantpivoting of said reflective surface in one direction about said firstaxis and then the opposite direction; a moving photosensitive mediumhaving a first dimension and a second dimension orthogonal to said firstdimension, and located to receive an image of said reflected light beamas it sweeps or traces across said medium along said first dimension assaid mirror device is resonantly pivoting about said first axis, saidphotosensitive medium moving in a direction along said second dimensionsuch that an image of a subsequent trace of light is spaced from aprevious trace; and a second driver for pivoting about said second axissuch that traces are received on said moving photosensitive medium alonga line substantially orthogonal to the movement of said photosensitivemedium.
 29. The printer of claim 28 wherein said photosensitive mediumis cylindrical shaped and rotates about an axis through the center ofsaid cylinder.
 30. The printer of claim 28 wherein said light beantraces on said medium are modulated in both directions such that saidprinter is a bi-directional printer.
 31. A display device comprising: alight source providing a beam of light; a first integrally formed devicecomprising a reflective surface portion positioned to intercept saidbeam of light, a support portion, and a first pair of torsional hingesattached to said reflective surface portion and extending to saidsupport portion for resonant pivoting about a first axis such that lightreflected from said reflective surface defines a first path; a firstdrive circuit for generating vibrational energy in said support portion,said vibrational energy inertially coupled through said first pair oftorsional hinges to said reflective surface portion to cause resonantpivoting of said first device about said first axis to provide aresonant beam sweep; a second device for rotating about a second axissuch that light from said reflective surface moves in a second directionsubstantially orthogonal to said first path; a display screen having afirst dimension and a second dimension orthogonal to said firstdimension, and located to receive a multiplicity of modulated imagelines of said reflected light beam as said beam sweeps across saiddisplay screen along said first dimension, each image line of saidmultiplicity being equally spaced from the preceding image line in adirection along said second dimension to generate an image frame; and asecond drive circuit for rotating said second device about said secondaxis such that said multiplicity of image lines are spaced across saiddisplay screen along a line substantially orthogonal to said resonantbeam sweep.
 32. The display device of claim 31 wherein said first andsecond devices together comprise an integrally formed single dual axismirror and wherein said support portion of said first device and saidsupport portion is a gimbals support pivotally attached to a supportmember by a second pair of torsional hinges and wherein said mirror ofsaid first device is attached to said gimbals support by said first pairof torsional hinges.
 33. The display device of claim 31 wherein saidfirst device comprises a first single axis torsional hinged mirror andsaid second device comprises a second single axis torsional hingedmirror, said second device positioned to intercept said beam of lightfrom said light source and reflect said light beam to said reflectivesurface of said first device.
 34. A display device comprising: a lightsource providing a beam of light; an integrally formed mirror devicecomprising a reflective surface portion positioned to intercept saidbeam of light from said light source, a first hinge arrangement forsupporting said reflective surface and for pivoting about a first axis,a gimbals portion and a second hinge arrangement, said gimbals portionattached to said first hinge arrangement and supported by a second hingearrangement for pivoting about a second axis substantially orthogonal tosaid first axis such that pivoting of said device about said first axisresults in light reflected from said reflective surface defining a firstpath, and pivoting of said device about said second axis results in saidreflective light moving in a second direction substantially orthogonalto said first path; a first driver for generating vibrational energyinertially coupled through said second hinge arrangement and throughsaid first hinge arrangement to said reflective surface portion to causeresonant pivoting of said reflective surface in one direction about saidfirst axis and then the opposite direction; a display screen having afirst dimension and a second dimension orthogonal to said firstdimension, and located to receive a multiplicity of modulated imagelines of said reflected light beam as it sweeps or traces across saiddisplay screen along said first dimension as said mirror device isresonantly pivoting about said first axis, each image line of saidmultiplicity being equally spaced from the preceding image line in adirection along said second dimension to generate an image frame; and asecond driver for pivoting about said second axis such that saidmultiplicity of image lines are spaced across said display screen alonga line substantially orthogonal to said resonant beam sweep.
 35. Amethod of providing an oscillating beam sweep across a target comprisingthe steps of: providing a reflective surface pivotally attached to andintegrally formed with a support portion by a first hinge arrangement,said reflective surface having a resonant frequency at which saidsurface pivotally resonates about said hinge arrangement; reflecting abeam of light from said reflective surface; locating said target tointercept said reflected beam of light; and inertially couplingvibrational energy to said reflective surface to cause said reflectivesurface to pivotally resonate about said first hinge arrangement suchthat said reflected beam of light continuously sweeps back and forthacross said target.
 36. The method of claim 35 wherein said step ofproviding comprises the step of providing a reflective surfaceintegrally formed with and pivotally attached to a support frame whereina first portion of said support frame is also integrally formed with andattached to a support structure and said step of providing furthercomprising locating at least one electrostatic plate a selected distanceform a second portion of said support frame and wherein said step ofinertially coupling further comprises the step of connecting analternating voltage between said electrostatic plate and said supportframe to generate vibration in said support frame.
 37. The method ofclaim 35 wherein said step of providing comprises the step of providinga reflective surface integrally formed with and pivotally attached to apair of support anchors and attaching a first portion of each of saidpair of support anchors to a support structure, and said step ofproviding further comprising locating at least one electrostatic plate aselected distance from a second portion of at least one of said pair ofsupport anchors and wherein said step of inertially coupling furthercomprises the step of connecting an alternating voltage to saidelectrostatic plate and at least one of said support anchors. step ofinertially coupling further comprises the step of connecting analternating voltage to said electrostatic plate and at least one of saidsupport anchors.
 38. The method of claim 35 wherein said step ofproviding further comprises the steps of providing a reflective surfaceintegrally formed with and pivotally attached to a support frame andwherein a first portion of said support frame is attached to a supportstructure, bonding a portion of piezoelectric material having a firstend and a second end to a second portion of said support frame, whereinsaid step of inertially coupling further comprises connecting analternating voltage to said first and said second end of said portion ofpiezoelectric material to generate vibrations in said support frame. 39.The method of claim 35 wherein said step of providing comprises the stepof providing a reflective surface integrally formed with and pivotallyattached to a pair of support anchors and attaching a first portion ofeach of said pair of support anchors to a support structure, and saidstep of providing further comprising bonding a portion of piezoelectricmaterial having a first end and a second end to a second portion of atleast one of said support anchors and wherein said step of inertiallycoupling further comprises connecting an alternating voltage to saidfirst end and said second end of said portion of piezoelectric materialto generate vibration in said support frame.
 40. The method of claim 35wherein said step of providing further comprises the step of locating apair of electromagnetic coils on each side of said first axis and spacedfrom said reflective surface and wherein said step of inertiallycoupling further comprises connecting an alternating voltage across saidpair of coils to generate vibration in said support frame.
 41. Themethod of claim 35 wherein said step of providing comprises the steps ofproviding a reflective surface integrally formed with and pivotallyattached to a gimbals portion by a first hinge arrangement for pivotingabout a first axis, and further comprising pivotally attaching saidgimbals portion to an integrally formed support member by a second hingearrangement for pivoting about a second axis orthogonal to said firstaxis, and said method further comprising the step of pivoting saidreflective surface about said second axis to orthogonally position saidreflected bean of light as said reflected beam of light sweeps back andforth across said target.
 42. The method of claim 35 wherein said stepof providing further comprises the steps of locating at least oneelectrostatic plate a selected distance from a portion of said supportmember and connecting an alternating voltage to said electrostatic plateand said support member to generate vibration in said support member,and wherein said step of inertially coupling comprises the step ofinertially coupling vibrational energy through said second hingearrangement to said gimbals portion and from said gimbals portionthrough said first hinge arrangement to said reflective surface.
 43. Themethod of claim 35 wherein said step of providing further comprises thesteps of bonding a portion of piezoelectric material having a first endand a second end to said support member and connecting an alternatingvoltage to said first end and said second end of said portion ofpiezoelectric material to generate vibration in said support member, andwherein said step of inertially coupling comprises the step ofinertially coupling vibrational energy through said second hingearrangement to said gimbals portion and from said gimbals portionthrough said first hinge arrangement to said reflective surface.